Method of continuous casting



Jan. 5, 1954 J L HUNTER 2,664,607

y METHOD OF CONTINUOUS CASTING Original Filed May 17, 1950 4 2Sheets-Sheet l Jan. 5, 1954 J. HUNTER METHOD OF CONTINUOUS yCASTINGOriginal Filed May 17, 1950 2 Sheets-Sheet 2 Both the launder i and box35 are made of a suitable refractory material to withstand the hightemperature of the molten metal. rihe box 35 is supported on ahorizontal shelf fill which is formed integrally with the supportingstructure of the machine, and the launder 34 is secured to the wall orother structure of the furnace well 32 adjacent to the tap hole 33. Thebox 35 is divided by a partition il into two chambers i2 and is whichfeed the two spouts 35 (Figure 4), and these chambers are connected byopenings lll with the channel of the launder 3d near the bottom thereof,so that the metal flowing down the launder is admitted to the chambers.

The casting machine 22 is seen to comprise a pair of endless chains ofarticulated, water cooled mold blocks til, each of said chains beingtrained around horizontally spaced pairs of drive sprockets 5| anddriven sprockets 62, and one of said chains being disposed directlyabove the other and Each of the mold blocks 6B is a massive block ofhard, dense cast iron or steel, ground on all sides and in the machineas shown, having two shallow channels 55 and 65 formed in the outer facethereof. Each of the channels 65, 65 constitutes one half of the moldcavity for one of the bars of metal cast by the machine, and when themating blocks of the adjacent courses of the top and bottom chains arebrought together in proper registration with one another, they form apair of laterally spaced, open end mold cavities of uniform crosssection that extend longitudinally through the center of the machine.Transverse alignment of the mating mold blocks within extremely closetolerances is obtained by means of small rectangular end plates 5l whichare securedby screws to opposite ends of each block in the top chain 63and project outwardly for a short distance beyond the outer face of theblock to form flanges that lit snugly down over the ends of thecompanionate block in the bottom chain 55.. The bottom block is thusconfined between the end plates 5l', and is prevented thereby fromshifting transversely with respect to the top block; hence the twoblocks are always maintained in accurate transverse alignment with oneanother during the period of their conjunction.

Each of the mold blocks is connected to the adjoining blocks by hingepins which project laterally beyond the ends of the blocks, andjournaled on the ends of the said pins are rollers 'i4 which run on theperipheral edges of rigidly supported side plates 15. Each of the sideplates 'I5 is elongated horizontally, with straight top and bottom edgesand semicircular ends having their centers of curvature at the axes ofthe sprockets 6| and 52. rlChe side plates 'I5 of each chain S3, 54 aremounted on a supporting structure Si) located at one side of the chainmold assembly, and are attached thereto by a pair of laterally spaced,thick-walled steel pipes '16 of large diameter which projecthorizontally outward from a side wall plate l5 of the supportingstructure 8i! between the sprockets 5| and 52. The structure Sil is madeup of heavy steel plates welded together at their edges to form aclosed, box-like 4 member of great strength and rigidity. The pipes 'I5are closed at their outer ends, and are secured by bolts 8| to thesupporting structure 8S, the said bolts passing all the way through thesupporting structure as shown in Figure 4.

The driving and driven sprockets 6|, 62 are welded or otherwise suitablyxed to drive shafts 85, between and immediately adjacent plates 15, thesaid shafts extending through circular openings in the plates. The outerend of the shaft 85 terminates in a threaded stud on which a nut 'IS isscrewed, and the latter is drawn up tight against a collar TI that bearsagainst the outside of the outer sprocket 6|. Each of the sprockets 5I,62 is rotatably supported on the structure BU.

A spur gear is mounted on the end of the upper shaft 85 where itprojects from the back of the supporting structure Bil, and is securedagainst rotation relative thereto by means of a key or the like. Acorresponding spur gear is secured to the lower sprocket drive shaft.The top gear Q5 is meshed with an idler gear 55, which is meshed, inturn, with another idler gear that is also meshed with the bottom spurgear, and the last-named idler gear meshes with a pinion G8. Pinion 9Bis driven by a sprocket IES through a friction clutch IilI, which isadapted to slip when overloaded, and thus protects the mold chains anddriving mechanism from damage in the event that something becomesjammed.

Trained around the sprocket |80 is a roller chain ||Il which extendsdownwardly to and is trained around a sprocket mounted on the driveshaft of an electric motor |I2. A second sprocket I I 5 (Figure 4) onthe motor shaft drives another chain l which is trained around a largesprocket I4 on shaft I I5, to drive the pinch rolls 2S. The electricmotor |2 also drives the rotatable heads of the coolant distributor 24,and to this end, a sprocket |20 is mounted on the bottom drive shaft 85,which drives a chain |2| that is trained around another sprocket (notshown) on a shaft |23.

Shaft |23 extends forwardly through the supporting structure Bil (asshown in Figure 3) and is operatively connected to the coolantdistributor mechanism 24 to drive the same. As described in detail inPatent No. 2,631,343, the coolant distributor 24 comprises a housing |25which supports two vertically spaced, rotatable heads |34 and |35, thatare driven from shaft |23 in the same direction and at the same rate ofspeed as their respective mold block chains S3 and 64. The heads |313,|35 are connected by flexible hoses I'I5 and I9! to inlet and outletttings on the ends of the mold blocks. A pump |64 driven by a motor |55circulates coolant from a reservoir tank |10, through swiveled fluidcouplings |59, heads |313, 135, inlet hoses N5, mold block coolantpassageways, return hoses lill, back into the tank |13, and out throughoverflow pipe |12.

On leaving the machine at the exit end thereof, the solidified bars ofmetal are guided laterally into the pinch rolls 25 between outer rolls223 and tandem inner rollers 22| (Figure li) which are rotatablysupported on a horizontal shelf 2.22 projecting laterally from thesupporting structure 85. The pinch rolls 25 comprise an upper roll 223and a lower roll 221i which extend transverse to the direction of travelof the cast bars, and which are rotatably supported at their ends inbearing blocks 225. The bearing blocks 225 are slidable verticallybetween laterally spaced pairs of guide posts 226, which are mounted ona horizontal a bridge rmember .23 l.

#accesar y shelf plate i'tt f projecting i laterally vfrom the v`sideAof the supporting structure its, .the `top Aends 4of each pair of posts.being,connected-together by Long bolts .232 extend upwardly through theshelf23, guideposts-ZZS, bridgemember Ito securefthe side frames into asolid structure. An adjusting .screw 233 is threaded` downwardly throughthe bridge member 22! and engages the top bearing block 225 to adjustthe spacing between the rolls 223,224.

The bottom rollV 224 is connected atitsback end to the sprocket shaft lI5 and is driven thereby in theclockvfise direction, as viewed in Figure2; the top roll 223 being driven by the bottom roll intheoppositeidirecticn and at thesamerate of speed through a pair ofintermeshed gears (not shown) which are enclosed within a housing 23,4(Figuresg and 4).

bestshown FiguresJ `3 `and 2, the .tworolls `223, 2f-2li are watercooled, l,and to this end 4rare provided withcylindrical bores 2,35(Figuref), through which va pipe :236 of somewhat smaller outsidediameter is passed. vFitted on extensions of the roll necksandpipes/Zbeyond the gear housing 23d are swivel couplings 248 whichdeliver Y' water to theinner pipe236 and exhaust the water rfrom thespace between ythe'pipe Aand the-walls of the bore The inlet sides ofthe couplings 22E ere connected to pipes 24| which are joined togetherand connected to the main Water pipe Il! while the outlet side of thecouplings is connected to a pipe 2h32 (Figures 1 and 3) that returns theused water to the tank i ll).

The rolls 223 and 224 have two important functions: iirst, they aredriven at a speed carefully computed to regulate the speed of the barsto the linear speed of the chains E3, 64, less the linear rate ofthermal contraction of the cast bars that has taken place between thepoint in the machine where the metal becomes solid and the point ofcontact of the rolls 223, 224; and second, they perform the work ofpushing the bars into the holding oven 36, thereby relieving the chains63, 54, of this relatively heavy load. The ilrstnamed function isimportant because of the low tensile strength of most metals attemperatures near the melting point. Aluminum, for example, ischaracteristically hot-short at temperatures just below its meltingpoint, and in the hot-short temperature range the tensile strength ofthe metal is substantially zero. The rapid cooling of the metal in thecasting machine causes a very considerable amount of shrinkage in thebar, and if the bar is allowed to leave the mold blocks at the samespeed as the linear travel of the chains 53, 612, the lengthwiseshrinkage of the bar within the mold cavities of the machine will causethe bar to pull apart or at least crack, in its weak, hot-short zone.The pinch rolls 223, 224 hold back on the bar so that the amount ofshrinkage is taken up, and the exit speed of the bar from the machine issomewhat less than the linear speed of the chains 53, 64. For example,when casting aluminum alloy with a coeiiicient of thermal expansion of.0000254 per degree centigrade, with a distance of 40 inches between thesolidication zone and the point of engagement of the bar by the pinchrolls, and temperature drop of 120 C., the cooling shrinkagetheoretically amounts to ,122 inch. Assuming that the casting machine isoperating at 60.00() inches per minute (5 ft. per min), the peripheralspeed of the pinch rolls would be not more than 59.878 in. per min. Inpractice, it would be desirable to operate the pinch rolls at a slightlyslower peripheral speed .tot accommodate any additional shrinkage Athat4nfii-ght'result from a slightly .greatertemperature `drop due to.colder coolantwater, slower operating ,speed ofthe machine, or=the like,The proper peripheralspeedof the vpinch rolls is obtainedbyzproportioning the sprockets Hs and llt so that a rotational: speedisl obtained which iscor- `rect iforthe .diameters of the rolls 223 and'224.

Thezsecond-@named function is important where long lengths of bar haveto be'pushedinto the oven. .In such instances, the work #required toovercomefriction of the bar sliding over its supports'within the `ovenmay exceed the pushing 'capacity of the casting machine, since the"machineihas only the friction of the moldblocks on the bars to drivethe latter, 'and in that case the mold blocks would merely skid alongthe vbars. -Thepinch rolls.223,22l maybe tightened'down ontofthe bars bythe adjusting screw233'tosecure ra powerfulfrictional grip thereon.

The pinch rolls 223, 221i thus cooperate y.with

' the castingmachine 221to perform the method'of' Bti continuous castingwhich forms the essence of' the Apresent invention. The method of vthein vention consists of the steps of pouringmolten` metalinto acontinuously traveling,-powerfdrivenz mold'which chills the metal into asolid`fbar,and then engaging vthe bar beyond the exitend of the mold, asby the pinch rolls 223, 224, and driving the same at a predeterminedlinear speed substantially corresponding to the speed at which thel moldis traveling, less the linear rate of thermal contraction of the castbar between the point of solidication and the point of drivingengagement by the pinch rolls. The bar is thus held back into the moldto an extent such that the metal in the hot-short zone is maintainedsubstantially without tension, and at the same time, the bar ispropelled beyond the exit end of the mold by the pinch rolls, entirelyindependent of the frictional engagement of the bar by the surfaces ofthe mold blocks.

As the bars leave the pinch rolls, they are engaged on their outer edgesby two guide rolls 25!) (Figures 3 and 4) which are supported on anarrow shelf 25| projecting laterally outward from the supportingstructure 8E) at the extreme end thereof.

Beyond the guide rolls 256, the bars pass through the flying shearcut-off 23, where they are automatically cut to predetermined lengthswhile continuing in motion. The flying shear cuto (best shown in Figures1 and 3) is essentially a hydraulically operated shear mounted on afreely movable carriage that is adapted to travel with the bars whilethe latter are engaged by the shear blades. The construction andoperation of the flying shear cut-off 28 is described in detail in myPatent No. 2,631,343, to which reference may be had.

The operation of the casting machine is believed to be self-evident fromthe foregoing description. When the machine is rst started up, theopenings M3 in the box 35 through which molten metal flows into thespouts 36 are blocked off, and the furnace is tapped. Molten metal isallowed to iill the chambers t2 and 43, and to overflow through a notch223 in the side of the box, running down a gutter 282 into pig molds,`until the launders 34 and box 35 have been thoroughly heated and thetemperature of the metal in the box is right for casting. The passages2l3 are then uncovered, and metal is allowed to ilow through the spouts36 into the mold cavities. 'I'he mold cavities are usually plugged witha block so as to prevent the metal from flowing along the mold cavityuntil the latter has been lled. These blocks are carried through themachine on the front ends of the bars, and drop 01T when the bars pushout of the machine at the exit end thereof. While the speed of themachine depends upon a number of variables, I have found that the mostsatisfactory operation for aluminum alloys is obtained with a chainspeed of approximately 5 feet per minute.

While I have shown and described in considerable detail the preferredcasting machine embodying the method of my invention, it will beunderstood that the method may be practiced by using other apparatus,and the present machine is merely illustrative.

I claim:

The method of continuously casting metal in bar form, comprising thesteps of introducing molten metal into the entrance end of acontinuously traveling, power driven mold, rapidly chilling the metal soas to solidify the same into a negrained metal bar, said bar beingpropelled by tractional engagement of the mold walls with the bar, andthen engaging the bar beyond the exit end of said mold and positivelydriving the same at a linear speed substantially corresponding to thespeed at which the mold is traveling, less the linear rate of thermalcontraction of the cast bar between the point of solidication and thepoint of driving engagement, the tractive forceexerted on said barbeyond the exit end of said mold opposing and exceeding the tractiveeiort of the mold walls, whereby the bar is held back into said mold toan extent such that the metal in the hotshort zone is maintainedsubstantially without tension, and whereby said bar is propelled beyondthe exit end of said mold independently of the frictional engagement ofthe bar by the surfaces of said mold.

JOSEPH L. HUNTER.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,865,443 Perry et al July 5, 1932 1,870,406 Douteur Aug. 9,1932 2,290,083 Webster July 14, 1942 2,565,959 Francis et al Aug. 28,1951 2,590,311 Harter et al Mar. 25, 1952 FOREIGN PATENTS Number CountryDate 273,311 Great Britain May 17, 1928

